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Effect of acoustic perturbation on particle dispersion in a swirl-stabilized pulverized fuel burner: Cold-flow conditions
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.ORCID-id: 0000-0003-1250-9683
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.ORCID-id: 0000-0002-1445-4121
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.ORCID-id: 0000-0002-0308-3871
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.ORCID-id: 0000-0001-6081-5736
Vise andre og tillknytning
2022 (engelsk)Inngår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 228, artikkel-id 107142Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Inter-particle distance and particle dispersion during gasification of biomass have been found to significantly affect soot emission. Consequently, enhanced particle dispersion decreases energy losses and the risk for blockages of downstream equipment, increasing the efficiency and reliability of entrained flow reactors (EFRs). In this work, we investigated the interactions between imposed acoustic oscillations and particle dispersion under non-reacting conditions in a co-axial burner for a lab-scale EFR. A flow of air, laden with pulverized stem wood particles (Norwegian Spruce) of three different sizes (63–112 μm, 200–250 μm, and 500–600 μm), was forced axially through the burner center tube at Reynolds numbers ranged from 800 to 1700, and loading ratio of 0.7–4.2. The influences on particle dispersion from variations of the Strouhal number (0.12–0.6), the pressure amplitude at synthetic jet cavity (0.5–4.0 kPap-p), the swirl number (0–2.3), and the center jet velocity (1.9–3.9 m s−1) were investigated. Post-processed shadowgraph images revealed the influence of acoustic perturbations, which generate large structures with high particle concentration for both swirling and non-swirling conditions. Time-averaged contour maps showed a significantly higher particle dispersion, quantified as dispersion angle, for higher values of forcing amplitude and swirl numbers, with a stronger influence from the forcing amplitude, especially at lower Stokes number.

sted, utgiver, år, opplag, sider
Elsevier, 2022. Vol. 228, artikkel-id 107142
Emneord [en]
Biomass, Acoustic excitation, Particle-laden flow, Particle dispersion, Gas-particle coaxial jets
HSV kategori
Forskningsprogram
Energiteknik
Identifikatorer
URN: urn:nbn:se:ltu:diva-88606DOI: 10.1016/j.fuproc.2021.107142ISI: 000749923000004Scopus ID: 2-s2.0-85121808061OAI: oai:DiVA.org:ltu-88606DiVA, id: diva2:1623514
Forskningsfinansiär
Swedish Energy Agency, 47485-1The Kempe Foundations, SMK-1632
Merknad

Validerad;2022;Nivå 2;2022-01-01 (johcin)

Tilgjengelig fra: 2021-12-29 Laget: 2021-12-29 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Inngår i avhandling
1. Particle dynamics during biomass devolatilization: Momentum exchange and particle dispersion
Åpne denne publikasjonen i ny fane eller vindu >>Particle dynamics during biomass devolatilization: Momentum exchange and particle dispersion
2022 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Devolatilization is a heat-driven thermochemical process in which a liquid or a solid fuel releases mass in the form of volatile compounds after drying, as a result of the combination of endothermic and exothermic reactions. It differs from pyrolysis in that it does not require an inert atmosphere and that the reactant must be either solid or liquid. Devolatilization is present in every industrial process involving high temperature thermochemical conversion of solid fuels, such as combustion or gasification.

Biomass devolatilization is a complex process which entangles dynamic changes in internal heat transfer with phase change and chemical kinetics. The higher the heating rate and the temperature at which devolatilization takes place, the more uncertain the outcome of these processes and the more challenging to measure. Furthermore, since devolatilization involves heat and mass transfer to its surroundings, this can also have an effect on the external conditions, for example by altering the surrounding gas temperature or composition, or by transferring momentum to the particle or the surrounding gas. The inherent uncertainty in biomass thermochemical properties and composition difficult the fundamental understanding even further.

Suspension firing of pulverised fuels is a technique applied to high temperature thermochemical conversion processes, in which a particle-laden gas flow is injected into a hot atmosphere. Due to the extreme heat transfer conditions, the particles exhibit a very fast heating rate and achieve quickly a very high temperature during the stage at which they devolatilize. Measurements of mass loss and composition under these conditions are difficult to achieve using laboratory equipment, such as thermogravimetric analysers.

The aim of this PhD thesis is to investigate the devolatilization of biomass particles under high heating rate conditions, by measuring their morphology and velocity dynamics while reacting in a hot laminar gas flow. The measurement techniques applied, allow a very fast sampling rate and, while they prevent a fundamental understanding of the underlying mechanisms of high temperature devolatilization. They provide valuable and practical knowledge that can be applied to realistic conditions and allow the introduction of uncertainties in biomass size, shape and composition. 

The work carried for this thesis provides experimental measurements of particle size, shape and velocity for a devolatilizing stream of biomass particles, using high-speed imaging diagnostics. An interesting phenomenon related to the interaction between devolatilization reactions and particle momentum is investigated in detail. Additional modeling and simulation work is provided, to assess the model’s performance and the importance of this phenomenon. Particle dispersion caused by this phenomenon is compared to the one achievable by active flow manipulation techniques, such as swirling and vortex generation.

This work provides important information regarding the complex fluid-solid interactions caused by the dynamics of biomass devolatilization from a stochastic and modelling and simulation point of view. Although these results are not directly applicable to industrially-realistic conditions, the methodology for this investigation can be applied to more complex flows and further work must be conducted to understand the mechanisms behind the phenomenon observed and the consequences for devolatilization. 

sted, utgiver, år, opplag, sider
Luleå: Luleå University of Technology, 2022
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Emneord
Biomass, devolatilization, rocketing, PIV, PTV
HSV kategori
Forskningsprogram
Energiteknik
Identifikatorer
urn:nbn:se:ltu:diva-88689 (URN)978-91-8048-005-5 (ISBN)978-91-8048-006-2 (ISBN)
Disputas
2022-03-17, E231, Luleå, 09:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2022-01-10 Laget: 2022-01-10 Sist oppdatert: 2022-02-28bibliografisk kontrollert
2. Experimental analysis of a pulverized biomass-fired entrained flow reactor under imposed acoustic oscillations
Åpne denne publikasjonen i ny fane eller vindu >>Experimental analysis of a pulverized biomass-fired entrained flow reactor under imposed acoustic oscillations
2022 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
sted, utgiver, år, opplag, sider
Luleå: Luleå University of Technology, 2022
Serie
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
HSV kategori
Forskningsprogram
Energiteknik
Identifikatorer
urn:nbn:se:ltu:diva-90097 (URN)978-91-8048-065-9 (ISBN)978-91-8048-066-6 (ISBN)
Presentation
2022-06-02, E231, Luleå Tekniska Universitet, Luleå, 10:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2022-04-13 Laget: 2022-04-12 Sist oppdatert: 2023-09-05bibliografisk kontrollert

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Llamas, Angel David GarciaChishty, Muhammad AqibUmeki, KentaroGebart, Rikard

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